In conventional cylinder locks of this type, the lamellae are guided in a diametral direction in transverse keyways formed in the rotor and are each provided with a return spring under the action of which they engage in the slots of the stator when the key is removed.
On the other hand, it has been proposed to make the lamellae in the form of discs which are not provided with return springs and of which the movements along two diameters at right angles to one another are guided by ball races formed in transverse dividing webs between which the lamellae amounted and which are integral with one another to form the rotor of the cylinder, this double movement of the lamellae being obtained by means of a cruciform key by way of four additional balls situated between the lamellae and each notch of the key.
The advantage of locks with lamellae displaceable in two directions at right angles to one another is that they have a large number of combinations which is dependent upon the number of lamellae and upon the number of notches in the two profiles of the cruciform key, which provides this lock with a high level of potential security. By contrast, the production and assembly of cylinders with lamellae displaceable in two directions are so complex that no practical embodiment has as yet been developed. In addition, the cruciform keys are not readily accepted for certain applications, in particular for safety locks for motor vehicles (door locks and antitheft locks), so that their use has been virtually confined to certain door locks.